A maximum torque current ratio control method of a variable frequency signal injection interior permanent magnet synchronous motor

Abstract

This invention discloses a method for controlling the maximum torque-to-current ratio (MTPA) of an embedded permanent magnet synchronous motor (PMSM) using variable frequency signal injection. Based on Space Vector Pulse Width Modulation (SVPWM), it utilizes the six basic vectors and two zero vectors of a three-phase bridge inverter to synthesize a reference voltage vector. By adjusting the duration of the synthesized vector within the six sectors, phase fluctuations are generated in the synthesized reference voltage vector, thereby generating a variable frequency disturbance signal with a frequency that is an integer multiple of the motor's base frequency, which is then injected into the motor. This disturbance signal causes the flux linkage vector amplitude and the current vector amplitude to fluctuate at the same frequency, and the ratio of these two values ​​determines the MTPA operating point. To identify the frequency of the disturbance signal at different motor base frequencies and effectively extract the corresponding high-frequency disturbance signal, the frequency of the disturbance signal is first identified through a frequency detection stage. This frequency is then set as the center frequency of the BPF and fixed into the filter expression, achieving adaptive extraction of the disturbance frequency.

Description

Technical Field

[0001] This invention relates to a method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting frequency conversion signals. Background Technology

[0002] Embedded permanent magnet synchronous motors (PMSMs) are gradually becoming the preferred solution in fields such as electric vehicles and high-performance servo drives due to their advantages such as high torque density, wide speed and constant power range, and high overload capacity. In response to national energy conservation and emission reduction policies, the maximum torque-to-current ratio control of embedded PMSMs has also become a research hotspot.

[0003] In recent years, scholars both domestically and internationally have conducted in-depth research on MTPA control of embedded permanent magnet synchronous motors, achieving fruitful results. These mainly include lookup table methods, extreme value search methods, and the most widely used high-frequency auxiliary signal injection method. The lookup table method is relatively simple to implement, but its drawbacks are also quite obvious, such as requiring a large amount of storage space and having poor robustness to motor parameters. The extreme value search method has strong robustness to motor parameters and is easy to implement, but the algorithm has a long convergence time. In the most widely used signal injection methods, a high-frequency, small-amplitude perturbation signal is usually artificially injected to track the MTPA point, which makes the high-frequency noise problem of the motor more prominent. Furthermore, most signal injection methods superimpose the signal on the front end of the PI controller, causing the frequency of the injected signal to be limited by the PI bandwidth. Although the space vector signal injection method injects the signal directly into the inverter, the frequency of the injected signal remains fixed. The frequency converter signal injection method ensures that the frequency of the injected signal does not interfere with the fundamental frequency as the motor speed increases. As the motor's fundamental frequency changes, the frequency of the injected signal also changes. However, during the extraction of the MTPA factor, the center frequency of the bandpass filter cannot keep up with the change in the injected signal frequency. This causes the bandpass filter to lose the frequency of the disturbance signal during sudden speed changes, leading to algorithm failure. Therefore, how to solve the problems existing in the signal extraction part of the above signal injection method has become an important research topic. Summary of the Invention

[0004] The present invention provides a method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting frequency conversion signals in order to solve the problems existing in the prior art.

[0005] The technical solutions adopted in this invention are as follows:

[0006] A method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting a frequency converter signal includes the following steps:

[0007] S1: The α and β axis voltages are fed into the SVPWM module. The SVPWM module divides the six sectors according to the motor fundamental frequency and determines the basic voltage vector used to synthesize the reference voltage vector. While keeping the amplitude of the reference voltage vector constant, the phase of the reference voltage vector is fluctuated by changing the duration of the basic voltage vector. A high-frequency disturbance signal with a frequency that is an integer multiple of the motor fundamental frequency is generated and injected into the motor.

[0008] S2: Calculate the frequency of the high-frequency disturbance signal based on the fundamental frequency of the motor, set the calculated frequency as the center frequency of the bandpass filter, and construct a frequency adaptive bandpass filter.

[0009] S3: The stator current amplitude carrying the high-frequency disturbance signal is sent to the frequency adaptive bandpass filter to obtain the high-frequency current component. The high-frequency current component is multiplied with the flux disturbance sinusoidal signal. After the high-frequency component is filtered out by the low-pass filter, the DC component containing the maximum torque current ratio criterion is obtained. The maximum torque current ratio angle is obtained by adjusting the integrator.

[0010] S4: The motor speed setpoint is compared with the motor speed feedback value, and the stator current amplitude is output through speed closed-loop control. The d-axis and q-axis currents are allocated according to the ratio of the stator current amplitude to the maximum torque current. The allocated d-axis and q-axis currents are compared with the corresponding current feedback values, and d-axis and q-axis voltage commands are generated through current closed-loop control. After obtaining the α-axis and β-axis voltage commands through Park inverse transformation, they are sent to the SVPWM module and finally drive the motor through the inverter.

[0011] Furthermore, in S1, the six sectors are divided as follows:

[0012] When the fundamental frequency of the motor is less than or equal to 50Hz, the vector action time of each of the six sectors is adjusted so that the reference voltage vector fluctuates six times the fundamental frequency of the motor.

[0013] When the fundamental frequency of the motor is greater than 50Hz and less than or equal to 100Hz, the six sectors are divided into three sector groups according to two adjacent sectors. The vector action time of each sector group is adjusted so that the reference voltage vector produces a fluctuation three times the fundamental frequency of the motor.

[0014] When the fundamental frequency of the motor is greater than 100Hz, the six sectors are divided into two sector groups of three adjacent sectors each. The vector action time of each sector group is adjusted so that the reference voltage vector produces a fluctuation twice that of the fundamental frequency of the motor.

[0015] Furthermore, in S1, when the reference voltage vector is located within the first sector, the reference voltage vector is synthesized using the basic voltage vectors U1 and U2. While maintaining the magnitude of the reference voltage vector unchanged, the expression for changing the duration of action of the basic voltage vectors U1 and U2 is as follows:

[0016] ,

[0017] in, and This represents the adjusted vector action time of the basic voltage vectors U1 and U2. and This represents the vector action time before adjustment. It is the gain coefficient, used to change the amplitude of the injected signal. The value is 1.5.

[0018] Furthermore, in S2, the expression for calculating the frequency of the high-frequency disturbance signal based on the fundamental frequency of the motor is as follows:

[0019] ,

[0020] in, Represents the frequency multiplier. The values ​​are 6, 3, and 2; f is the fundamental frequency of the motor. This refers to the motor speed, expressed in r / min. This represents the number of pole pairs of the motor.

[0021] Furthermore, in S2, the transfer function expression of the frequency adaptive bandpass filter is:

[0022] ,

[0023] in, The quality coefficient represents the filter. The value is 40.

[0024] Furthermore, in S3, the process of multiplying the high-frequency current component with the sinusoidal signal of the magnetic flux disturbance and filtering out the high-frequency component using a low-pass filter is as follows:

[0025] Assume the sinusoidal signal of the magnetic flux disturbance is The amplitude of the disturbed stator current is approximately... Multiplying the two and performing trigonometric transformations, we get:

[0026]

[0027] Where A represents the amplitude of the high-frequency signal, and K is a scaling factor, used to filter out high-frequency signals by a low-pass filter. After the high-frequency terms, the criterion including the maximum torque-to-current ratio is obtained. The DC component.

[0028] Furthermore, in S4, the distribution expressions for the d-axis current setpoint and the q-axis current setpoint are as follows:

[0029] ,

[0030] in, Indicates the stator current amplitude. This indicates the maximum torque-to-current ratio angle.

[0031] Furthermore, in S4, the speed closed-loop control includes:

[0032] The speed error is obtained by comparing the setpoint motor speed with the feedback motor speed, and the output stator current amplitude is adjusted by the PI controller.

[0033] The current closed-loop control includes: obtaining the d-axis current error by subtracting the d-axis current setpoint from the d-axis current feedback value, obtaining the q-axis current error by subtracting the q-axis current setpoint from the q-axis current feedback value, and the d-axis current error and q-axis current error are adjusted by a PI controller to output d-axis voltage command and q-axis voltage command.

[0034] The present invention has the following beneficial effects:

[0035] (1) This invention adopts a frequency conversion signal injection method. The disturbance signal is generated by adjusting the duration of the basic voltage vector through the SVPWM module. The frequency of the injected signal changes with the motor's fundamental frequency, which can avoid mutual interference between the injected signal and the motor's fundamental frequency to a certain extent. At the same time, this invention addresses the characteristic that the injection frequency changes with the fundamental frequency in the frequency conversion injection scheme. It uses the motor's fundamental frequency to calculate the frequency of the disturbance signal in real time and sets this frequency value directly as the center frequency of the bandpass filter, thus constructing a frequency adaptive bandpass filter. This allows the center frequency of the filter to change with the frequency of the disturbance signal, solving the problem of the bandpass filter losing the effective frequency during sudden changes in motor speed. This enhances the dynamic convergence performance of the maximum torque-current ratio algorithm under sudden speed changes and ensures the flexibility and reliability of disturbance frequency extraction.

[0036] (2) In this invention, the flux disturbance signal is directly generated by the actively injected voltage disturbance and is synchronized with the fluctuation of the voltage vector. The change in the stator current amplitude is only a passive response caused by the disturbance. Therefore, there is no need to calculate and filter the flux separately. The maximum torque-current ratio point can be obtained by directly multiplying the known injected sinusoidal signal as the flux disturbance sinusoidal signal and the current response signal, which simplifies the signal processing flow. Attached Figure Description

[0037] Figure 1(a) is the main block diagram of the frequency-adaptive BPF-based variable frequency signal injection embedded permanent magnet synchronous motor MTPA control method.

[0038] Figure 1(b) is a block diagram of the signal processing module.

[0039] Figure 1(c) is a block diagram of the frequency adaptive BPF structure.

[0040] Figure 2 Vector synthesis diagram of variable frequency signal injection method (sixth harmonic).

[0041] Figure 3(a) is a comparison of the effect of the reference voltage vector when a sixth-harmonic signal is injected.

[0042] Figure 3(b) shows the waveforms of the MTPA angle and current amplitude under the condition that the motor speed is 300 r / min and the torque is 9 Nm.

[0043] Figure 3(c) shows the torque and current angle waveforms when the motor speed is 300 r / min and the torque changes abruptly from 8 Nm to 10 Nm.

[0044] Figure 3(d) shows i d =0 controls the switching of the MTPA control diagram. Detailed Implementation

[0045] The invention will now be further described with reference to the accompanying drawings.

[0046] Figure 1(a) shows the overall control block diagram of the system. The motor speed setpoint ω... ref With motor speed feedback value ω m The motor speed error is obtained through comparison. This error is then adjusted by the speed loop PI controller, and the output is used to obtain the stator current amplitude of the motor. The stator current amplitude Angle ratio to the maximum torque current obtained The current is fed into the current distribution module, and after calculation, the d-axis current setpoint i can be obtained. dref and q-axis current setpoint i qref Compare it with the d-axis current feedback value i dm and q-axis current feedback value i qm The difference is calculated to obtain the current error, which is then adjusted by the current loop PI controller to output the d-axis voltage command u. d and q-axis voltage command u q Subsequently, the α-axis voltage command u is obtained through Park's inverse transformation. α and β-axis voltage command u β This voltage is fed into a space vector pulse width modulation (SVPWM) circuit to synthesize a reference voltage vector, which is then used by the inverter to output three-phase current to drive the motor. On the motor side, the motor speed ω...m The rotational speed is measured by a photoelectric position encoder and forms a closed loop, then the corresponding rotor position θ is obtained through an integration module. m It is then fed into the Park transform.

[0047] The SVPWM module used in this invention is the SVPWM modulation module disclosed in patent 202010863954.0 (CN112054735A). The specific functions and principles of this SVPWM module will not be described in detail in this application.

[0048] Figure 1(b) shows the block diagram of the MTPA signal processing module. The α-axis current i... α and β-axis current i β The stator current amplitude was calculated. The signal is then fed into a frequency-adaptive bandpass filter. Since the flux linkage fluctuation originates from an actively injected disturbance signal, its variation pattern remains consistent with the voltage vector fluctuation, while the current amplitude change is a passive response signal caused by this disturbance. Therefore, there is no need to separately calculate and filter the flux linkage. The known injected sinusoidal signal is directly used as the flux linkage disturbance sinusoidal signal, multiplied by the filtered stator current response signal, and then filtered by a low-pass filter to remove high-frequency components. The obtained DC component contains the maximum torque-to-current ratio criterion, which is then fed into an integrator to obtain the MTPA point.

[0049] Figure 1(c) shows the block diagram of the frequency adaptive bandpass filter. First, the frequency ω of the current disturbance signal is calculated using the motor's fundamental frequency. h The obtained disturbance signal frequency will be directly fed into the bandpass filter. The transfer function expression of the frequency adaptive bandpass filter is:

[0050] ,

[0051] in, The quality coefficient represents the filter. A value of 40 can be taken. Therefore, even if the motor's fundamental frequency changes, the disturbance frequency also changes. However, through the above expression, the center frequency of the bandpass filter will follow the change of the disturbance frequency, thus enabling the filter to adaptively track the disturbance frequency.

[0052] This invention discloses a method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting a frequency converter signal, comprising the following steps:

[0053] S1: Injection of frequency conversion signal.

[0054] The α and β axis voltages are fed into the SVPWM module, which divides the motor into six sectors based on the motor's fundamental frequency to determine the basic voltage vector used to synthesize the reference voltage vector. While keeping the amplitude of the reference voltage vector constant, the phase of the reference voltage vector is fluctuated by changing the duration of the basic voltage vector, generating a high-frequency disturbance signal with a frequency that is an integer multiple of the motor's fundamental frequency, which is then injected into the motor.

[0055] The method of dividing the six sectors based on the fundamental frequency of the motor is as follows:

[0056] When the fundamental frequency of the motor is less than or equal to 50Hz, the vector action time of each of the six sectors is adjusted so that the reference voltage vector fluctuates six times the fundamental frequency of the motor.

[0057] When the fundamental frequency of the motor is greater than 50Hz and less than or equal to 100Hz, the six sectors are divided into three sector groups according to two adjacent sectors. The vector action time of each sector group is adjusted so that the reference voltage vector produces a fluctuation three times the fundamental frequency of the motor.

[0058] When the fundamental frequency of the motor is greater than 100Hz, the six sectors are divided into two sector groups of three adjacent sectors each. The vector action time of each sector group is adjusted so that the reference voltage vector produces a fluctuation twice that of the fundamental frequency of the motor.

[0059] Assuming the reference voltage vector is located within the first sector, and the reference voltage vector is synthesized using the basic voltage vectors U1 and U2, the expression for changing the duration of the basic voltage vectors U1 and U2 while keeping the magnitude of the reference voltage vector constant is as follows:

[0060] ,

[0061] in, and Represents the adjusted vector action time of the basic voltage vectors U1 and U2; and The vector duration before adjustment of the basic voltage vectors U1 and U2; It is the gain coefficient, used to change the amplitude of the injected signal. 1.5 is acceptable.

[0062] like Figure 2The diagram shows the reference voltage vector synthesis of the frequency conversion signal injection method, taking a sixth-harmonic frequency as an example. When the motor's base frequency is less than 50Hz, six sectors are used to synthesize the reference voltage vector. When the reference voltage vector is located in a certain sector, the duration of the synthesized reference voltage vector between two adjacent vectors is changed, causing the reference voltage vector to generate an arc-shaped fluctuation outside the sector, fluctuating once in each sector, thus generating a disturbance signal six times the motor's base frequency.

[0063] S2: Construction of a frequency-adaptive bandpass filter.

[0064] The frequency of the high-frequency disturbance signal is calculated based on the fundamental frequency of the motor, and the calculated frequency is set as the center frequency of the bandpass filter to construct a frequency adaptive bandpass filter.

[0065] The frequency of the current disturbance signal is calculated using the motor's base frequency. Please refer to the following formula:

[0066] ,

[0067] in, Represents the frequency multiplier. The values ​​are 6, 3, and 2; f is the fundamental frequency of the motor. This refers to the motor speed, expressed in r / min. This represents the number of pole pairs of the motor. In the test prototype used, the value was 4. Taking a motor speed of 100 r / min as an example, substituting n = 100 r / min into the formula, the frequency ω of the disturbance signal can be obtained. h =80πrad / s.

[0068] The obtained disturbance signal frequency will be directly fed into the bandpass filter. The transfer function expression of the frequency adaptive bandpass filter is:

[0069] ,

[0070] in, The quality coefficient represents the filter. 40 is acceptable.

[0071] S3: Maximum torque current ratio angle extraction.

[0072] The stator current amplitude carrying the high-frequency disturbance signal is sent to the frequency adaptive bandpass filter to obtain the high-frequency current component. The high-frequency current component is multiplied by the flux disturbance sinusoidal signal. After the high-frequency component is filtered out by the low-pass filter, the DC component containing the maximum torque-current ratio criterion is obtained. The maximum torque-current ratio angle is obtained by adjusting the integrator.

[0073] The MTPA point is actually determined through the relationship between flux linkage amplitude, current amplitude, and torque, which is expressed as:

[0074] ,

[0075] This expression can be further derived to obtain the partial derivative relationship between the stator current amplitude and the stator flux linkage amplitude, as follows:

[0076] ,

[0077] This expression can be used as the MTPA criterion. In the formula, Indicates electromagnetic torque; Indicates the number of pole pairs of the motor; Represents the stator flux linkage vector; Represents the stator current vector; βMTPA represents the stator current angle, which is the angle between the stator current vector and the d-axis. βMTPA is the stator current angle corresponding to the maximum torque-current ratio control. This represents the load angle, which is the angle between the stator flux linkage and the d-axis.

[0078] The flux linkage fluctuations originate from actively injected disturbance signals, and their variation pattern remains consistent with the voltage vector fluctuations. The changes in current amplitude, on the other hand, are the passive response signal caused by this disturbance. Therefore, there is no need to separately calculate and filter the flux linkage; the MTPA point can be obtained by directly multiplying the known injected sinusoidal signal as the flux linkage disturbance sinusoidal signal with the current response signal.

[0079] The overall extraction process of the MTPA point can be derived as follows. Assume the expression for the flux linkage disturbance caused by the voltage disturbance is:

[0080] ,

[0081] The amplitude of the disturbed stator current can then be expressed as:

[0082] ,

[0083] After passing through a frequency-adaptive bandpass filter, signals containing disturbance frequencies in the magnetic flux and current can be extracted. Multiplying the two together yields:

[0084] ,

[0085] From the above formula, the MTPA criterion It appears on the right side of the equation and can be extracted using a low-pass filter.

[0086] S4: Dual closed-loop control and motor drive.

[0087] The motor speed setpoint is compared with the motor speed feedback value, and the stator current amplitude is output through speed closed-loop control. The d-axis and q-axis currents are allocated according to the ratio of the stator current amplitude to the maximum torque current. The allocated d-axis and q-axis currents are compared with the d-axis current feedback value and q-axis current feedback value, respectively, and the d-axis and q-axis voltage commands are generated through current closed-loop control. After obtaining the α-axis and β-axis voltage commands through Park inverse transformation, they are sent to the SVPWM module and finally drive the motor through the inverter.

[0088] The expression for allocating the d-axis current setpoint and the q-axis current setpoint is as follows:

[0089] ,

[0090] in, This indicates the amplitude of the stator current.

[0091] Speed ​​closed-loop control includes: setting the motor speed setpoint ω ref With motor speed feedback value ω m The speed error is obtained by comparison, and the output stator current amplitude is adjusted by the PI controller. .

[0092] Current closed-loop control includes: setting the d-axis current setpoint i dref With d-axis current feedback value i dm The difference is used to obtain the d-axis current error, and the q-axis current setpoint i is used as the reference. qref The q-axis current error is obtained by subtracting the q-axis current feedback value iqm. The d-axis current error and the q-axis current error are then adjusted by a PI controller to output the d-axis voltage command u. d and q-axis voltage command u q .

[0093] Figure 3(a) shows a comparison of the reference voltage vector effect when a six-fold frequency harmonic signal is injected. Compared with the reference voltage vector before the signal injection, the reference voltage vector after the signal injection produced 6 fluctuations in one cycle, indicating that the disturbance signal was successfully generated and injected into the system as expected.

[0094] Figure 3(b) shows the MTPA angle and current amplitude waveforms under the condition of motor speed of 300 r / min and torque of 9 Nm. To clearly demonstrate the MTPA point tracking performance of the proposed method, the current angle was first adjusted from 90° to 135°. After 40 seconds, the MTPA algorithm took effect. It can be seen that as the algorithm ran normally, it successfully tracked the MTPA point. At the same time, the current angle corresponding to the manually set MTPA operating point was 112°, while the tracked MTPA angle was 113.5°, and the current amplitude decreased from 21.5A to around 21.5A, verifying the effectiveness of the algorithm.

[0095] Figure 3(c) shows the motor speed and d-axis current waveforms under the condition that the motor speed abruptly changes from 300 r / min to 600 r / min and the torque is 10 Nm. As the motor speed abruptly changes from 300 r / min to 600 r / min, it is easy to see that the motor's d-axis current remains at around -8 A. This proves that even if the motor's fundamental frequency changes from 20 Hz to 40 Hz, the frequency adaptive bandpass filter in the MTPA signal extraction module can still effectively track the frequency of the disturbance signal. Therefore, the MTPA algorithm can always be effective, directly proving the effectiveness of the frequency adaptive bandpass filter.

[0096] Figure 3(d) reflects the situation caused by i d The experimental results of switching from =0 control to the frequency converter signal injection MTPA method are shown in Figure 3(d). As can be seen from Figure 3(d), when the motor speed is 600 r / min and the load torque is 9 Nm, under the condition that the output torque remains unchanged, the phase current of the motor decreases from 12.5A to 9.8A. Therefore, the MTPA implementation effect of this method is better.

[0097] In summary, this invention, based on the space vector pulse width modulation (SVM) algorithm, utilizes the six basic vectors and two zero vectors of a three-phase bridge inverter to synthesize a reference voltage vector. By adjusting the duration of the synthesized vector within the six sectors, phase fluctuations are generated in the synthesized reference voltage vector, thereby generating a variable frequency disturbance signal with a frequency that is an integer multiple of the motor's base frequency and injecting it into the motor. This disturbance signal causes the flux linkage vector amplitude and the current vector amplitude to fluctuate at the same frequency, and the ratio of these two values ​​determines the MTPA operating point. To identify the frequency of the disturbance signal under different motor base frequencies and effectively extract the corresponding high-frequency disturbance signal, the frequency of the disturbance signal is first identified through a frequency detection stage. This frequency is then set as the center frequency of the bandpass filter and fixed into the filter expression, achieving adaptive extraction of the disturbance frequency. This invention, on the one hand, allows the injected signal frequency to vary with the motor base frequency, achieving decoupling between the injected frequency and the motor base frequency; on the other hand, it allows the center frequency of the bandpass filter to adaptively follow the injected frequency, thereby enhancing the dynamic convergence performance of the MTPA algorithm under sudden speed changes and ensuring the flexibility and reliability of disturbance frequency extraction. This method is applicable to MTPA control of all embedded permanent magnet synchronous motors based on SVPWM.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting a frequency conversion signal, characterized in that: Includes the following steps: S1: The α and β axis voltages are fed into the SVPWM module. The SVPWM module divides the six sectors according to the motor fundamental frequency and determines the basic voltage vector used to synthesize the reference voltage vector. While keeping the amplitude of the reference voltage vector constant, the phase of the reference voltage vector is fluctuated by changing the duration of the basic voltage vector. A high-frequency disturbance signal with a frequency that is an integer multiple of the motor fundamental frequency is generated and injected into the motor. S2: Calculate the frequency of the high-frequency disturbance signal based on the fundamental frequency of the motor, set the calculated frequency as the center frequency of the bandpass filter, and construct a frequency adaptive bandpass filter. S3: The stator current amplitude carrying the high-frequency disturbance signal is sent to the frequency adaptive bandpass filter to obtain the high-frequency current component. The high-frequency current component is multiplied with the flux disturbance sinusoidal signal. After the high-frequency component is filtered out by the low-pass filter, the DC component containing the maximum torque current ratio criterion is obtained. The maximum torque current ratio angle is obtained by adjusting the integrator. S4: The motor speed setpoint is compared with the motor speed feedback value, and the stator current amplitude is output through speed closed-loop control. The d-axis and q-axis currents are allocated according to the ratio of the stator current amplitude to the maximum torque current. The allocated d-axis and q-axis currents are compared with the corresponding current feedback values, and d-axis and q-axis voltage commands are generated through current closed-loop control. After obtaining the α-axis and β-axis voltage commands through Park inverse transformation, they are sent to the SVPWM module and finally drive the motor through the inverter.

2. The method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting a frequency conversion signal as described in claim 1, characterized in that: In S1, the six sectors are divided as follows: When the fundamental frequency of the motor is less than or equal to 50Hz, the vector action time of each of the six sectors is adjusted so that the reference voltage vector fluctuates six times the fundamental frequency of the motor. When the fundamental frequency of the motor is greater than 50Hz and less than or equal to 100Hz, the six sectors are divided into three sector groups according to two adjacent sectors. The vector action time of each sector group is adjusted so that the reference voltage vector produces a fluctuation three times the fundamental frequency of the motor. When the fundamental frequency of the motor is greater than 100Hz, the six sectors are divided into two sector groups of three adjacent sectors each. The vector action time of each sector group is adjusted so that the reference voltage vector produces a fluctuation twice that of the fundamental frequency of the motor.

3. The method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting frequency conversion signals as described in claim 1, characterized in that: In S1, when the reference voltage vector is located within the first sector, the reference voltage vector is synthesized using the basic voltage vectors U1 and U2. While keeping the magnitude of the reference voltage vector constant, the expression for changing the duration of action of the basic voltage vectors U1 and U2 is as follows: ， in, and This represents the adjusted vector action time of the basic voltage vectors U1 and U2. and This represents the vector action time before adjustment. It is the gain coefficient, used to change the amplitude of the injected signal. The value is 1.

5.

4. The method of claim 1, wherein the maximum torque current ratio control method of a variable frequency signal injection interior permanent magnet synchronous motor is characterized by: In S2, the expression for calculating the frequency of the high-frequency disturbance signal based on the fundamental frequency of the motor is as follows: ， wherein, represents the number of frequency multiplication, is 6, 3, 2; f is the fundamental frequency of the motor; is the motor speed, in r / min; is the number of motor pole pairs.

5. The method of maximum torque current ratio control of an interior permanent magnet synchronous motor with variable frequency signal injection according to claim 1, characterized in that: In S2, the transfer function expression of the frequency adaptive bandpass filter is: ， wherein a quality factor of the representative filter, takes the value 40.

6. The method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting frequency conversion signals as described in claim 1, characterized in that: In S3, the process of multiplying the high-frequency current component with the sinusoidal flux disturbance signal and then filtering out the high-frequency component using a low-pass filter is as follows: Assume the sinusoidal signal of the magnetic flux disturbance is The amplitude of the disturbed stator current is approximately... Multiplying the two and performing trigonometric transformations, we get: Where A represents the amplitude of the high-frequency signal, and K is a scaling factor, used to filter out high-frequency signals by a low-pass filter. After the high-frequency terms, the criterion including the maximum torque-to-current ratio is obtained. The DC component.

7. The method of maximum torque current ratio control of an interior permanent magnet synchronous machine with variable frequency signal injection according to claim 1, characterized in that: In S4, the distribution expressions for the d-axis current setpoint and the q-axis current setpoint are as follows: ， wherein, denotes the stator current amplitude, denotes the maximum torque current ratio angle.

8. The method for controlling the maximum torque-to-current ratio of an embedded permanent magnet synchronous motor by injecting a frequency conversion signal as described in claim 1, characterized in that: In S4, the speed closed-loop control includes: The speed error is obtained by comparing the setpoint motor speed with the feedback motor speed, and the output stator current amplitude is adjusted by the PI controller. The current closed-loop control includes: obtaining the d-axis current error by subtracting the d-axis current setpoint from the d-axis current feedback value, obtaining the q-axis current error by subtracting the q-axis current setpoint from the q-axis current feedback value, and the d-axis current error and q-axis current error are adjusted by a PI controller to output d-axis voltage command and q-axis voltage command.

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